Aureus

Aureus (plural: aurei) was a type of gold coin in ancient Rome. It had the same value as 25 denarii silver coins. An aureus was the same size as a denarius, but it weighed more because gold is more dense.

The front an back of an aureus from the year 193

Aureus often displayed the bust of the reigning emperor, while the reverse featured various deities, personifications, or significant events. The aureus remained in circulation until the early 4th century AD, when Emperor Constantine I's monetary reforms introduced the solidus.

Gold coins like the aureus and solidus were vital to the Roman economy, used for large transactions, military payments, and as a store of value. Their high intrinsic value contributed to economic stability, facilitating efficient tax collection and troop payments, which were essential for sustaining the vast Roman Empire.